Ferroelectricity can exist in elemental phases as a result of charge transfers between atoms occupying inequivalent Wyckoff positions. We investigate the emergence of ferroelectricity in two-dimensional elemental materials with buckled honeycomb lattices. Various multi-bilayer structures hosting ferroelectricity are designed by stacking-engineering. Ferroelectric materials candidates formed by group IV and V elements are predicted theoretically. Ultrathin Bi films show layer-stacking-dependent physical properties of ferroelectricity, topology, and metallicity. The two-bilayer Bi film with a polar stacking sequence is found to be an elemental topological ferroelectric material. Three and four bilayers Bi films with polar structures are ferroelectric-like elemental polar metals with topological nontrivial edge states. For Ge and Sn, trivial elemental polar metals are predicted. Our work reveals the possibility of design two-dimensional elemental topological ferroelectrics and polar metals by stacking-engineering.
@article{arxiv.2309.14609,
title = {Elemental topological ferroelectrics and polar metals of few-layer materials},
author = {Hu Zhang and Lulu Zhao and RuiFeng Zhang and Chendong Jin and Ruqian Lian and Peng-Lai Gong and RuiNing Wang and JiangLong Wang and Xing-Qiang Shi},
journal= {arXiv preprint arXiv:2309.14609},
year = {2023}
}